I'm using this plugin , I want to set language as French fr, for that I use formatter: new L.Routing.Formatter(language: 'fr') like you can see the code bellow :
L.Routing.control({
waypoints: [L.latLng(48.8534, 2.3488), L.latLng(44.837789, -0.57918)],
routeWhileDragging: true,
show: true,
formatter: new L.Routing.Formatter({ units: 'metric', language: 'fr' }),
autoRoute: true
}).addTo(this.mapInstance);
But, the result is always in English 'en'.